Selenium is an essential trace element for human body. Selenocysteine is the active site of glutathione peroxidase, phospholipid-hydroperoxide glutathione peroxidase, thioredoxin reductase, methionine sulfoxide reductase and indothyronine deiodinase, and participates in the antioxidation and energy metabolism of the organism. In addition, high doses of selenium has growth suppressing and killing activities on tumor cells.
It has been known that the survival situation of the patient in the Intensive Care Unit was significantly improved by injecting high doses of sodium selenite, and the death rate is reduced largely. Since sodium selenite is a selenium compound with strong toxicity, and the margin between the beneficial dose and the toxic dose is quite narrow, there is a need in clinic to replace sodium selenite with a different selenium form, which has the same bioactivity to high doses of sodium selenite but with lower toxicity.
Chemotherapy may result in side effects such as leucocyte reduction, diarrhea, vomit, edema and the like and even threaten the life of the patients. These side effects seriously restrict the dosage and therapeutic efficacy of chemotherapy agents. It has been reported that sodium selenite can depress the toxicity of cisplatin without compromising its activity, which makes it possible to use high doses of cisplatin to enhance the anti-tumor effect of cisplatin. However, the doses of sodium selenite in these studies were all in the toxic level (0.5-2 mg Se/kg), and the therapeutic efficacy will be attenuated after long-term co-administration of sodium selenite and chemical agents. Since the margin between the beneficial and toxic dose of selenium is quite narrow, only selenium compounds with lower toxicity can ensure the safe application for supplementing selenium at pharmacologic doses and treating tumors with the co-administration of chemical agents.
Sodium selenosulfate is an unstable inorganic selenium compound, and thus does not have a commercially available product. It was used widely for the preparation of nano-materials containing selenium. For example, sodium selenosulfate was used to prepare nano-sized copper selenide, cadmium selenide, lead selenide and the like. Generally, sodium selenosulfate was prepared by mixing elemental selenium power with sodium sulfite with a molar ratio of 1:3 to 1:6 and refluxing at a temperature of 80-100° C. for 2-4 hours. It is of prime importance for the stable time of the newly generated sodium selenosulfate that the sodium sulfite presents in excess, and the more sodium sulfite presents, the longer the stable time is. In general, the newly generated sodium selenosulfate is used immediately for the preparation of selenium nanomaterials. Sodium selenosulfate is a selenium compound, and there is no any report as to its Se-supplementing effect and biological functions related to selenium.